The École Polytechnique alumn network — known to its members simply as "X" — is the second of Pour la Joie's founding communities. The choice was not accidental: among the founders are graduates of the school, and they wanted to test the Joies first within a network they knew well.

Alumns have always been active for the sake of the community, but the younger generations tend to be critical of what appears to be a selfish network of influence. What better use of the Joies than to recognize students and alumns for what they do selflessly for each other, and stress what they do for the benefit of society?

Alumns can subscribe rights to issue new Joies — directly, or via a donation to MerciX, a new alumn group dedicated to fostering gratitude among the Polytechnique community. These rights are then gifted to student organizations to welcome new students on campus, or to thank students engaged in community activities. Alumn groups can also bestow medals — Joies with a limited private effigy — either to reward special dedication to their studies, or to honor their talents for organizing selfless activities.

In turn, students can use some of their Joies to recognize the alumns who volunteer to mentor them, or to thank their former professors for their dedication.